This project utilizes a successful national chronic disease data bank system (aramis) to develop a systematic technology assessment program in rheumatic disease. This data system currently tracks 10,000 patients with arthritis, contains information from 50,000 encounters, and has 20,000 patient-years of follow-up. Data banks include university centers (Stanford, Cincinnati), population-based samples (Saskatoon), surgical patients (UCSF, Stanford), private practice patients (Phoenix, Wichita), multiple institutions (SCCS), and pediatric patients (Cincinnati). The system operates on an IBM 370/166 computer at Stanford. The TOD software package is also used for the national Stroke and Coma data banks. National communications are established via the Telenet system. The data stored and the retrieval capabilities provide unique strengths for systematic technology assessment, defined broadly. Two major concepts are crucial. First, there is the problem of external validity (generalizability) of medical knowledge. Technology is developed and evaluated on special populations of patients and under especially favorable conditions. As a result, indications for the clinical decision in the community tend to be less selective than desirable. The chronic disease data bank surveys the community and can evaluate the degree of generalizability. Second, the data bank can systematically analyze the marginal benefit of new developments. Instead of asking whether a test, procedure, or mediation conveys benefit, the stricter question is addressed as to whether the development offers additional benefit over optimal alternatives. Together with the data bank, these two concepts provide a powerful tool with which to identify the unselective use of technology. This project will serve as a model for the use of the chronic disease data bank in technology assessment, in analysis of marginal benefit, in surveillance for problems from the use of technologies in the community, and for determination of the external validity of traditional information sources.